Post-installed anchor
A post-installed anchor is set into hardened concrete after the pour (mechanical or chemical), unlike a cast-in fastening; structural ones are designed under AS 5216.
Ask Chalkline about this →A post-installed anchor is an anchor set into hardened concrete after the pour, by drilling a hole and fixing into it, as opposed to a cast-in fastening placed in the formwork before the pour. Post-installed anchors split into two families: mechanical anchors, which grip by expansion or by cutting a thread (the torque-controlled sleeve and wedge anchors, drop-ins, and screw anchors), and chemical anchors, which bond a threaded rod into the hole with a resin.
Most fixings on a job are post-installed, because the structure is poured first and things are bolted to it later. The trade-off versus cast-in is that the concrete is already there, so the anchor relies on the drilled hole, the edge distances, and the concrete’s condition (cracked or uncracked) for its capacity, which is more variable than a fastening cast into fresh concrete. That is why structural post-installed anchors are engineered: their design sits under AS 5216, which sets the capacity calculation and the spacings, and the chosen anchor product must be prequalified (or carry a European Technical Assessment) to be used. NCC 2022 calls up AS 5216 for any post-installed anchor in a structural application on a Class 1 home.
For a structural fixing (post base, balustrade-to-slab, plant mount, retaining-wall connection) use the anchor type, size, embedment, and edge distance on the engineer’s schedule, not a hardware-shop equivalent, and drill, clean, and set it to the manufacturer’s instructions. For light non-structural brackets a standard expansion anchor is usually fine. See anchors and chemical anchors.
Also known as: Drilled-in anchor, retrofit anchor, post-fixed anchor.
Category: Fixings / Anchors.
Related
See also
References
- AS 5216:2021 Design of post-installed and cast-in fastenings in concrete, Standards Australia (verified 2026-05-29)
- ABCB NCC 2022 Housing Provisions clause 2.2.4(6) (verified 2026-05-29)
Last updated: 2026-05-30. Verified: 2026-05-29. Quarterly review for currency.